2D Rotation Trig

2D Rotation Trig

December 23, 2007 in Devlog, Javascript
Written by: Dag Jonny Nedrelid

I made this little script to play with sine and cosine to perform a 2D rotation. These are trigonometric functions to measure the ratio between the hypotenuse and the adjacent, or opposed line from θ. sine and cosine can be calculated in 2 ways, either dividing lines with hypotenuse, or through feeding a calculating function the θ.

In this script the rotation is made around the ‘would be’ z-axis in a 3D environment. As we keep looping the angle θ value in radian up to 2π(6.28)(360°), sine and cosine relationship/ratio values will keep changing accordingly. So, in math when you want to know the exact length of the θ’s opposite line, you multiply hypotenuse with its sine, in our case the coordinate Y. Multiply hypotenuse with co-sinus, and you get the actual length of the adjacent line as well, in our case the coordinate X. Hypotenuse becomes the range(line) from θ to the coordinates X/Y, ie. the radius.

Click here to open the script in a new window.

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My name is Dag Jonny Nedrelid. I'm an IT consultant and computer programmer who lives in Southern Norway. Computers have been one of my hobbies and line of work since 1995.

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